Froth flotation machine



Dec. 8, 1936. PATEK 2,063,751

FROTH FLOTAT ION MACHINE Filed Sept. 13, 1934 Maw M ATTORNEY.

Patented Dec. 8, 1936 UNITED STATES PATENT orrics 2,063,751 rao'rn no'ra'rror: mom

John Mark Patek. Milwaukee, Wis. Application September 13,1934, Serial No. 743,923

4 Claim 'This invention relates to machines for froth flotation, or for similar processes wherein agitation and aeration are desired. The invention resides in a machine wherein the air required for aeration is drawn into the cell by the action of an impeller, which at the same time causes a circulation of the contents of the cell, the impeller being closely approached by members causing high turbulence and through agitation, together with very intimate mixing of' air, and producing a circulation of the contents of the cell in a vertical plane, causing the contents to move generally across the bottom, up one side of the cell, across the top in the direction of the overflow lip and then downwardly along the other side of the cell to the starting place.

He'retofore a wide variety of flotation machines have been employed, having for their purpose the production of thorough agitation and intimate admixture of air. To accomplish this it has been found that a substantial amount of power is required and mechanical means for the provision of this power have been elaborate. Usually a rather extensive superstructure is employed to carry the power-transmission system. This necessitates strengthening of .the cell structure in order that the superstructure be properly supported. Furthermore, the superstructure encumbers that part of the cell where the most significant part of the process is taking place. Many of the cells now in use also produce a motion in the contents which is destructive of the froth, such as a swirling motion, which carries froth around the top of the cell without assisting in its removal. In the machine of this invention no superstructure is employed. The main support for the mechanical drive system may be derived from the foundation upon which the cells rest. The top of the machine is entirely open to access at all times and provision for removal of froth may be made at the most advantageous location. No strengthening of the cell enclosure for the support of a superstructure is necessary.

In the machine of this invention the contents 5 of the cell are not only thoroughly agitated and a very thorough admixture of air provided, but the direction of general circulation of the contents is such as to preserve the froth during itsremoval. The surface fluid of the contents of the machine of this invention moves in a direction toward the overflow lip and at the same time carries replenishing air which continuously rises through said fluid, repairing the froth. The rapid return of the liquid from the upper part of the pulp at the back of the cell toward the lower portion of the cell below the overflow lip causes the rising bubbles to be carried toward the overflow lip and to bubble upward into the froth. 1 The machine of this invention is bestdescribed by reference to the accompanying drawing, wherein Fig. 1 shows a cross-sectional view of the machine arranged as a duplex cell;

Fig. 2 shows a top plan view of the machine shown in Fig. 1;

Fig. 3 is a partial sectionof the portion of the cell indicated by the section line 3-3 in Fig. 2; .Fig. 4 is a diagrammatic view showing three duplex cells and the manner of making both the flow and mechanical connection thereof.

The machine of this invention may be constructed in single or multiple units and the form shown in the drawing is of a duplex arrangement thereof. As shown in Fig. 1, the machine consists of two complete cells I and 2 formed at one structural unit having an impeller 3 in. cell i and an impeller 4 in cell 2. Although the impellers 3 and 4 may be independently driven, they are shown inthe drawing as connected by the main shaft 5 to which said impellers are secured so that they will rotate therewith. The main shaft is arranged to rotate in bearings 6 and I, which are sealed by stufiing-boxes 8 and 9 so that when the machine is idle there shall be no loss of fluid. The shaft 5, as shown in Fig. 4, may be adapted to extend through othercells.

The impellers 3 and l are surrounded by closely approaching shrouds l and H, which direct fluid away from the impeller in the direction of the arrows and also prevent short-circuiting of the flow, although any desired amount of shortcircuiting may be produced by limiting the extent of the shroud. The shrouds, however, serve an additional purpose in that they are placed close to the tips of the impellers so that a high degree of turbulence is created when the impellers are rotated. Placed directly behind each impeller and close to the same are the diffuser cones i2 and I3. These cones are in communication with the atmosphere through the riser pipes l4 and I5, which extend outside of the cell to a point above the liquid level, not shown. The riser pipes l4 and I are also provided with regulating valves i3 and [1 so that the amount of air admitted may be regulated. It is to be understood that while the machine of this invention is in operation the entering air excludes all pulp and fluid from the space behind the cones I2v and I3 so that the bearings 6 and I are free from wear due to the action of the pulp.

Within the diffuser cones l2 and i3 and mounted upon the main shaft 5 are the rotor cones l8 and I9, which may be provided with surface vanes, the latter being arranged so that a narrow gap will exist between the rotors and the diffuser cones. Due to this narrow gap, inconsistencies in the low pressure area behind the impellers 3 and 4 are without effect upon the air supply and a'continuous and regular flow of air is produced.

The cell enclosure consists of a bottom 26 from which there rises in each cell curved ends 2| and 22. The curved ends rise in an easy curve and finally merge in a division wall 23. Facing the walls 2! and 22 and the division wall 23 are side walls 24 and 25 which slope inwardly toward the shrouds I0 and II, forming in the bottom of the cells a somewhat hopper-shaped structure. The cell enclosure is completed by the end walls 26 and 2? through which the drive and aeration mechanism enters. The shape and arrangement of the walls of the enclosure shown facilitates operation, although any enclosure will serve the purpose and modifications may produce specific advantages.

On one side of the cell i and connected to the division wall 23 is a launderbox 28 having therein an adjustable weir 29, regulated by regulating wheel 30. As shown in Fig. 1, by the section line passing through the regulating wheel, the contents of cell 2 may escape upwardly and over the weir 29 into the launder chamber and thence be carried away through the outlet 3!. The cell 2 is fed by material escaping from cell i through an opening 32 in the division wall 23. This opening is placed in the division wall on the side opposite the side occupied by the weir box 28. In this manner the fluid entering through opening 32 is prevented from being short-circuited and discharged into the Weir box before thorough treatment in cell 2 is obtained. Cell I receives feed through a feed-pipe 33 which enters behind the impeller I2 so that thorough mixing with the cell contents is immediately obtained.

The froth produced in the cell escapes over lips 34 and 35 into the troughs 36 and 31, which, as shown in Fig. 2, may feed into a main trough 38.

A cell of this invention has been operated successfully even in the separation of cassiterite from garnet in a natural ore. In such a case when the cells above described are operated, ma-

terial is fed in throughthe feed-pipe 33 until the liquid level reaches the edge of the weir 29. The weir 29 is then regulated to preserve the liquid level at the distance below lips 34 and 35 that is desired under the rate of feeding through feedpipe 33 which is prevailing. While this is being done impellers 3 and 4 are driven by shaft 5 and the regulating valves I6 and I7 adjusted to create the proper amount of aeration. When this condition has been established the cell will continue to operate without further attention. The agitation and aeration, provided the proper pulp is being fed and proper reagents are being employed, will produce a froth containing a concentrate, which rises to the surface and forms a layer which moves toward the lips 34 and 35, whence it flows into the discharge troughs 36 and 31. This is caused by the direction of the flow of fluid directly below the surface and no scraping, lifting, or pushing mechanism is generally necessary to assist in the removal of the froth. It may, at times, be advantageous to extend the back walls 26 and 21 of the cells backwardly a considerable distance in order that the pushing influence of the circulating fluid be somewhat minimized, in

the event that it is too vigorous, or the usual baffles which are sometimes employed to quiet the liquid near the lip may be employed. Throughout the circulating liquid, air is continuously rising and this is equally true of the liquid near the lip. This continuously rising of air in the liquid near the lip helps preserve the froth until the very moment it is discharged.

This invention has been described in connection with a machine showing two complete cells in a twin or duplex arrangement. It is to be understood, however, that single cells, representing half of the duplex unit, will function as a single cell in the manner of the usual single cell flotation machine and that limitation to a duplex unit is not intended. The duplex unit, however, has many advantages, one of which is represented in Fig. 4, where several duplex machines are shown arranged in series with a single main drive-shaft 5 passing through all of the cells, thus reducing the mechanical drive equipment to the most simple form. When so arranged the cells may, furthermore, be connected one to another, as far as flow is concerned, in a very rational and simplifled manner.

The manner in which the weir-box 28 is arranged takes advantage of the kinetic energy of the circulating fluid so that step-down or gravity connections between cells, or the like, are not necessary and the tailings will flow from machine to machine standing on the same level. This is due to the fact that the approach to the overflow is substantially a smooth continuation of the curvature of the side against which fluid from the impeller impinges, and also due to the I manner in which the pulp is fed to the intake side of the impeller.

This invention has been described in connection with certain forms and figures. It is intended, however, that the protection of Letters Patent to be granted hereunder be not unnecessarily limited thereby, but extend to the full scope of the invention as expressed within the terms of the claims appended hereto.

What I claim as my invention is:

1. In an apparatus for flotation machines for inducing aeration and agitation, the combination comprising a rotatable shaft extending within a flotation machine enclosure, a stator casing of conical form surrounding and axially placed with respect to said shaft and occupying a position in the lower portion of said enclosure, airadmitting means communicating with said stator and extending to a point outside of said enclosure, a conical rotor mounted on said shaft to turn therewith positioned within said stator to form a thin conical space therewith, an impeller adjacent said rotor and mounted on said shaft to turn therewith, said impeller being provided with blades intersecting the conical surface of said rotor extended, and a shroud surrounding said impeller.

2. In an apparatus for flotation machines for inducing aeration and agitation, the combination comprising a stator shell entering a wall of a flotation enclosure and fixedly secured with respect thereto, a bearing fixed with respect to said stator, a rotatable shaft mounted to rotate in said bearing and extending into said enclosure, means for admitting air to the interior of said stator, a rotor of form complementary to said stator mounted upon said shaft to rotate there.- with and spaced apart from said stator, an impeller comprising helical blades mounted upon said shaft adjacent to said rotor and fixedly secured to said shaft to rotate therewith, and a shroud surrounding said impeller.

3. In an apparatus for flotation machines for inducing aeration and agitation, a rotatable shaft extending within the flotation machine, a stator casing having an open end surrounding said shaft in the lower portion of said enclosure, an air-admitting means communicating with said stator and extending to a point outside of said enclosure, a helical impeller mounted on said shaft to turn therewith positioned beyond the open end of said stator to impel a flow of fluid from said stator in a direction parallel with said shaft, and a rotor within said stator mounted on said shaft to turn therewith.

4. In an apparatus for flotation machines for inducing aeration and agitation, a rotatable shaft extending within the flotation machine, a stator casing having an open end surrounding said shaft in the lower portion of said enclosure, an air-admitting means communicating with said stator and extending to a point outside of said enclosure, a helical impeller mounted on said shaft to turn therewith positioned beyond the open end of said stator to impel flow o! fluid from said stator in a direction parallel with said shaft, a rotor within said stator mounted on said shaft to turn therewith, and a shroud surrounding said impeller.

JOHN MARK PA'I'EK. 

